U.S. Pat. No. 4,253,533 discloses a drilling tool fitted with two runners made of elastomer and arranged diametrically, and, between the latter, a plurality of cutting edges made of diamond or a comparable material. The height of these runners is less than that of the cutting edges, with the result that only the ends of these cutting edges project outward from the outer surface of the runners. Accordingly, penetration of the cutting edges into the stratum is limited to a depth at most equal to the distance by which they extend beyond the runners. As a result, the cutting edges undergo only stresses that are much weaker that the forces they would have underdone had the entire length thereof penetrated into the rock.
However, these runners prove totally ineffective in absorbing the vibrations generated on the tool during drilling operations.
Patent No. EP 0 532 869 discloses a drilling tool containing a cavity in which a feed duct supplying an irrigation fluid empties, said cavity comprising a thin wall which incorporates an orifice through which the fluid can flow to the outside, and an opening in which a flat cylindrical element made of an elastomer is set in position. When acted upon by the pressure of the irrigation fluid in the cavity, the elastomer element undergoes deformation in the manner of a diaphragm, and the exterior surface thereof forms fluid-tight contact with the wall of the newly-drilled stratum, said contact, when the stratum is ductile, having the effect of compressing said exterior surface and protecting it from the impact generated by the irrigating fluid. Here, too, it can be seen that the elastomer block cannot dampen the vibrations of the tool.